The present invention pertains to pavement markings. More particularly, the present invention relates to pavement markings to including wear resistant protuberances.
Pavement markings are used on roadways to display traffic lanes and other traffic information to motor vehicle drivers. Very often pavement markings are retroreflective so that motor vehicle drivers can vividly see the markings at nighttime. Retroreflective pavement markings have the ability to return a substantial portion of incident light towards the source from which the light originated. Light from motor vehicle headlamps is returned toward the oncoming vehicle to illuminate, e.g., the boundaries of the traffic lanes for the motor vehicle driver.
In view of the important purpose served by pavement markings, investigators have continuously attempted to make various improvements to them. Indeed, the pavement marking art is replete with patented disclosures; see for example U.S. Pat. Nos.: 5,676,488; 5,670,227; 5,593,246; 5,286,682; 5,227,221; 5,194,113; 5,087,148; 4,988,555; 4,988,541; 4,969,713; 4,685,824; 4,490,432; 4,388,359; and 4,117,192.
Known retroreflective pavement markings typically include a rubber base sheet that contains pigments and fillers. Optical elements and/or skid-resistant particles are typically secured to a base sheet by being embedded therein or are secured thereto by a bonding material or binder. Pigments and fillers typically are dispersed throughout the base sheet for a number of reasons, including reducing cost, improving durability, and providing conformability. Pigments have also been placed in the bonding material to enhance visibility of the pavement marking and as part of the retroreflective mechanism.
When the pavement marking is retroreflective, it may include a raised pattern of protuberances on the upper surface of the base sheet to provide a more effective orientation for retroreflection and/or to elevate the optical elements above any water or other liquids on the roadway, thereby enhancing reflectivity of the pavement marking under wet conditions; see, for example, U.S. Pat. Nos. 5,227,221; 5,087,221; 5,087,148; 4,969,713; and 4,388,359.
As the spacing between the raised patterns of protuberances has been increased to improve retroreflectivity by reducing shadowing effects (see, e.g., U.S. Pat. No. 5,670,227), the susceptibility of the pavement marking to snowplow damage has increased. The damage is thought to be caused by the digging action of the snowplow blade as it falls into the valley areas between protuberances and then strikes the sides of the protuberances.
As a result, a need exists for a pavement marking including raised protuberances that is resistant to snowplow damage.
The present invention provides pavement markings and methods of making pavement markings including elongated protuberances that overlap along the longitudinal axis to improve the wear-resistance of the pavement markings to, e.g., snowplow blades or other objects moved across the pavement marking.
In one aspect, the present invention provides a pavement marking including base sheet having first and second major surfaces, the base sheet having a longitudinal axis and a width generally perpendicular to the longitudinal axis; a plurality of first protuberances projecting from the first major surface of the base sheet; and a plurality of elongated protuberances projecting from the first major surface of the base sheet; wherein the plurality of elongated protuberances overlap along the longitudinal axis of the pavement marking such that a cross-section taken transverse to the longitudinal axis of the pavement marking intersects at least one of the elongated protuberances.
In another aspect, the present invention provides a pavement marking including a base sheet having first and second major surfaces, the base sheet having a longitudinal axis and a width generally perpendicular to the longitudinal axis; a plurality of first protuberances projecting from the first major surface of the base sheet, wherein at least some of the first protuberances are substantially identical in shape and are located in a substantially regular repeating pattern; and a plurality of elongated protuberances projecting from the first major surface of the base sheet, each of the elongated protuberances having a major axis and a minor axis with the major axes of at least some of the elongated protuberances being aligned with the longitudinal axis of the pavement marking, wherein at least some of the elongated protuberances are substantially identical in shape and are located in a substantially regular repeating pattern; wherein the plurality of elongated protuberances overlap along the longitudinal axis of the pavement marking such that a cross-section taken transverse to the longitudinal axis of the pavement marking intersects at least one of the elongated protuberances.
In another aspect, the present invention provides a method of manufacturing a pavement marking by forming a plurality of first protuberances projecting from a first major surface of a polymeric continuous web base sheet having a longitudinal axis and a width generally perpendicular to the longitudinal axis; and forming a plurality of elongated protuberances projecting from the first major surface of the base sheet; wherein the plurality of elongated protuberances overlap along the longitudinal axis of the pavement marking such that a cross-section taken transverse to the longitudinal axis of the pavement marking intersects at least one of the elongated protuberances.
These and other features and advantages of the invention are more fully shown and described in the drawings and detailed description of this invention, where like reference numerals are used to represent similar parts. It is to be understood, however, that the drawings and description are for the purposes of illustration only and should not be read in a manner that would unduly limit the scope of this invention.